1. Field of Invention
The present invention relates to charge pumps, and more particularly, to a low-supply-voltage charge pump.
2. Description of Related Art
Charge pumps are used to generate a higher or greater magnitude voltage from a lower or lesser magnitude voltage. Charge pumps can be used, for example, in power converters, which are essential for many modern electronic devices. Power converters are typically implemented using one or more switching devices, such as transistors, which are turned on and off (or driven) to deliver power to the output of the converter.
For some power converters, there is a need to drive the switching devices even when the input supply (gate) voltage is close to threshold voltage of the switching devices. If the supply voltage is particularly low (e.g., 1V), charge pumps according to previous designs either fail to provide the requisite driving voltage due to pump-stage switch losses or alternately require complex structure. Furthermore, the problem of low input voltage is compounded when loading conditions increase current demand (i.e., heavy loads).
Moreover, in many applications the output voltage of a charge pump may be regulated to a fixed voltage; thus, the voltage across each pump stage is reduced (regulated) to a voltage less than the open-loop or unregulated value. As such, regulation reduces the individual pump-stage voltage available for gate drive.